Submodule 5: Most Common Western Rangelands Weeds

Diffuse Knapweed

Diffuse knapweed (Centaurea diffusa) is a biennial forb that can grow to about 2 feet (0.8 m) tall. Flowers, which grow in clusters at the end of stems, are white to pink or lavender and surrounded by spine-like bracts that are yellowish-green with a beige fringe. A single, erect stem generates several spreading branches holding buff greenish-grey leaves. The stem leaves are stalkless and decrease in size from the bottom to the top of the plant. The plant first forms a low rosette with long slender leaves. It can remain in this form for one to several years. After sufficient growth, it will bolt, or grow a tall, flowering stem with its characteristic stalkless, smaller leaves.

Diffuse knapweed stand (photo courtesy Larry Howery)